N. Nakaso et al., MEASUREMENT OF ACOUSTIC REFLECTION COEFFICIENTS BY AN ULTRASONIC MICROSPECTROMETER, IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 41(4), 1994, pp. 494-502
An ultrasonic microspectrometer (UMSM) was developed in order to evalu
ate the elastic properties of a solid specimen at a small spot on its
surface. In this system, spherical-planar-pair (SPP) lenses were used,
by which the acoustic reflection coefficient of a liquid/solid interf
ace was measured as a function of the incident angle in the frequency
range from 20 to 140 MHz. Using a specimen of fused quartz whose mater
ial constants were well known, the measurement accuracy was examined.
The phase velocity of a leaky Rayleigh wave was obtained from the phas
e change of the reflection coefficient with 0.4% accuracy in this freq
uency range. For a specimen of steel with a large acoustic attenuation
, bulk attenuation factors and their frequency dependence were success
fully estimated by computer-fitting of the reflection coefficient. As
an example of anisotropic materials, the reflection coefficient of X-c
ut quartz was also measured. Measured phase of the reflection coeffici
ent was in good agreement with numerical calculation.